Encephalitis lethargica is a viral encephalitis, the peculiarity of which is a two-phase course, the presence of pathological drowsiness in combination with oculomotor disorders and other neurological symptoms. In the chronic phase, extrapyramidal disorders usually prevail. Diagnosis is carried out using clinical analyses, EEG, ultrasound, REG, cerebrospinal fluid studies, MRI of the brain. Disease is difficult to treat. Detoxification and dehydration, antiviral and symptomatic therapy are carried out, corticosteroids, psychotropic and antiparkinsonian agents are used.
General information
Encephalitis lethargica was first described in detail in 1917 by the Austrian neurologist Economo, for which he received his second name in practical neurology — encephalitis Economo. From the time of the First World War until 1926, encephalitis lethargica in the form of epidemic outbreaks was often found in Western Europe. The disease often led to a fatal outcome. Nowadays, encephalitis Economo is rare and only as individual clinical cases.
In its course, encephalitis lethargica goes through 2 stages: acute and chronic. The first proceeds with signs of acute inflammation of the brain substance, the second — as a progressive degenerative brain disease with predominantly extrapyramidal disorders and mental changes. The time interval separating the acute and chronic stages of encephalitis varies from several months to 10 years.
Causes
Encephalitis lethargica refers to viral encephalitis. However, its causative agent has not yet been isolated, which is associated with its weak resistance in the external environment. Presumably, the transmission of the virus is carried out by an airborne mechanism. Once in the nasopharynx, the virus with the blood and lymph flow penetrates into the brain, where it causes a pronounced inflammatory reaction. The affected area, as a rule, is the brain stem and basal nuclei. In the acute stage, microscopy detects muff-like perivascular infiltration, proliferation of glious elements, sometimes in the formation of nodules. In the chronic stage, encephalitis lethargica is characterized by degeneration and death of ganglion cells with the formation of gliose scars in their place. These processes are most pronounced in the pale ball and the black substance.
Symptoms
Encephalitis Economically debuts with general infectious symptoms: bruising, fever, myalgia, headache. The period of increased body temperature takes about 2 weeks. At this time, neurological symptoms manifest. There is pathological drowsiness — hypersomnia. Patients tend to sleep a lot, fall asleep in all situations and in the most uncomfortable positions. Upon forced awakening, the patient falls asleep again. In some cases, insomnia is observed, more often it alternates with hypersomnia. Sleep disorders can be represented by a disorder of the normal sleep-wake rhythm, in which the patient sleeps during the day and cannot sleep at night.
Along with hypersomnia, the pathognomonic sign distinguishing encephalitis lethargica is the lesion of the oculomotor nerves. A partial lesion is characteristic, manifested by insufficiency of the function of individual muscles innervated by the oculomotor nerve. Patients often complain of deterioration or blurred vision, which is associated with diplopia or accommodation disorder. Anisocoria, drooping of the upper eyelid, vertical paralysis of the gaze may be observed. In some cases, the abductor nerve is affected, which leads to the appearance of strabismus.
Sleep disorders and oculomotor symptoms characterize encephalitis lethargica in its classic version. However, other neurological disorders may also occur: dizziness, vestibular ataxia, nystagmus, nausea and vomiting, manifestations of autonomic dysfunction (hyperhidrosis, vasomotor lability, hypersalivation, etc.). Sometimes in the acute stage, extrapyramidal disorders are observed, which are more characteristic of the chronic phase of encephalitis. These can be both hyperkinesis (athetosis, eye cramp, myoclonia, blepharospasm) and symptoms of secondary parkinsonism (amemia, hypokinesis, rigidity). It is possible to develop hypothalamic syndrome, cerebellar ataxia, hydrocephalus, psychosensory disorders (hallucinatory syndrome, change in shape perception). In severe cases, encephalitis lethargica is accompanied by disorders of cardiac activity, respiratory rhythm, deep disorder of consciousness (coma).
The acute stage can last up to a month. Recently, clinical cases of acute encephalitis Economo have mainly an abortive form. Their clinic is similar to the course of ARVI and includes only episodes of hypersomnia or other sleep disorders, transient diplopia, sometimes tics in the facial and cervical muscles or hiccups lasting several days due to myoclonic diaphragm cramps.
Encephalitis lethargica of the chronic stage develops in 35-50% of patients after a different period of time after the symptoms of the acute phase subside. It often occurs without previous symptoms of acute encephalitis. It is characterized by progressively increasing signs of damage to the extrapyramidal system, mainly by the type of akinetic-rigid syndrome with a clinical picture of secondary Parkinsonism. There is a decrease and slowing of motor activity, hypomimia, low-expressive speech, mental retardation, loss of interest in the events taking place. The neurological status is dominated by a generalized plastic increase in muscle tone. Tremor of the hands and secretory disorders typical of Parkinson’s disease are possible. In rare cases, paroxysms of narcolepsy are observed. Endocrine disorders may occur: hyperthyroidism, adiposogenital dystrophy, diabetes insipidus, obesity, menstrual cycle disorders.
Diagnostics
It is not so easy to diagnose encephalitis lethargica, with the exception of classic cases with hypersomnia and oculomotor disorders. In the acute phase, it is necessary to carry out differential diagnosis with serous meningitis and tick—borne encephalitis, in the chronic phase – with Parkinson’s disease, intracerebral tumor, encephalopathy, atherosclerosis of cerebral vessels, leukodystrophy.
For the purpose of differential diagnosis and diagnosis, general clinical analyses, EEG, ultrasound of the vessels of the head or REG, MRI of the brain, lumbar puncture are carried out. In the acute phase, signs of the inflammatory process, hypochromic anemia are determined in the blood test. Examination of the cerebrospinal fluid reveals lymphocytic pleocytosis, a slight increase in the concentration of sugar and protein. Diffuse changes are noted on the EEG, slow activity prevails. MRI allows you to visualize the foci of degeneration and glious scarring in the basal structures and trunk.
Treatment
Encephalitis lethargica is difficult to treat in any phase. In the acute period, detoxification, antiviral, dehydration, symptomatic therapy is carried out; it is possible to prescribe glucocorticosteroids, serum convalescents. Chronic encephalitis with Parkinsonian syndrome is regarded by a neurologist as an indication for the appointment of antiparkinsonian treatment: levodopa, trihexyphenidyl. In case of mental disorders, psychotropic drugs are resorted to. However, their appointment requires special care, since they can aggravate extrapyramidal disorders.
Forecast
In severe cases (about 30%), the acute phase of encephalitis lethargica can lead to death due to heart failure or respiratory dysfunction. Often, after acute encephalitis, residual symptoms are noted: headache, asthenia, insomnia, sleep-wake rhythm disturbances, depression. Children may have mental changes, hypothalamic syndrome, oligophrenia. Chronic encephalitis lethargica usually has a progressive course, although in some cases it is stabilized. In terms of recovery, the prognosis is unfavorable. The death of patients occurs due to cachexia or infectious diseases.
